Re the earlier comments about poor climb performance:
I don't understand these comments, after looking at the hyperlinked pictures. If those pictures were of the incident (and clearly #4 is the only engine not producing some smoke), then the climb angle shown appears quite acceptable to me. At a guess, climb angle exceeded 5 degrees.
Given the sky in the background and lack of cumulogranite in the pictures, I would suspect that ATC warnings of low altitude were quadrant based, not departure alley based.
FARs/JARs do not require huge climb angles in the event of engine failure. The performance shown in the pics would have been good for all engines performance for some previous generations (including early 747s at max gross on hot days).
From much earlier days, my recollection of climb performance on three Wright R3350s was that one had to average VSI readings to be sure one was in fact climbing.
Looks like a well handled incident with relatively low resultant risk.